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Electrolytic  Separations  Possible  With 
a  Rotating  Anode 


JTHESIS 

Presented  to  the  Faculty  of    the  Department    of    Philosophy  of  the 

University  of  Pennsylvania,   in   Partial  Fulfilment  of  the 

Requirements  for  the  Degree  of 

Doctor  of  Philosophy, 


BY 
DONALD  S.  ASHBROOK, 

PHILADELPHIA,  PA. 
1904 


PHILADELPHIA 

THE  JOHN  C.  WINSTON  CO. 

1904 


Electrolytic  Separations  Possible  With 
a  Rotating:  Anode 


THESIS 

Presented  to  the  Faculty  of    the  Department    of    Philosophy  of  the 

University  of  Pennsylvania,  in  Partial  Fulfilment  of  the 

Requirements  for  the  Degree  of 

Doctor  of  Philosophy, 


BY 
DONALD  S.  ASHBROOK, 

PHILADELPHIA,  PA. 
1904 


^e; 


. 


PHILADELPHIA 

THE  JOHN  C.  WINSTON  CO. 

1904 


cto 


5 


This  work  was  undertaken  at  the  suggestion  of  Dr. 
Edgar  F.  Smith.  The  author  takes  this  opportunity 
to  thank  him  for  his  many  kindnesses  and  personal 
interest  during  the  six  years  in  which  he  has  been  a 
student. 


INTRODUCTION. 

A  year  ago,  Exner*  working  in  this  laboratory  demon- 
strated that  by  using  a  high  current  density  and  great 
pressure  with  a  rotating  anode  it  was  possible  to  deter- 
mine fourteen  metals  in  the  electrolytic  manner  much 
more  rapidly  than  had  ever  been  done  previously  The 
deposits  were  in  all  instances  most  satisfactory.  These 
results  constituted  an  important  advance  in  electro- 
chemical analysis.  The  objection  once  put  forward,  that 
too  much  time  was  necessary  in  such  work,  was  com- 
pletely removed.  Indeed  Exner's  investigation  has 
wholly  revolutionized  electro-analysis.  However,  there 
remained  the  question  as  to  how  far  this  procedure  would 
lend  itself  to  the  separations  of  the  several  metals.  This 
point  became  the  guiding  thought  in  the  investigation 
here  presented. 

The  apparatus  and  method  of  procedure  have  been 
fully  described  and  amply  developed  by  Exner,  so  that 
they  need  not  be  again  entered  upon,  but  the  separations 
which  were  successful  and  have  value  will  now  be  described 
in  such  detail  as  to  guide  all  persons  who  may  be  desirous 
of  repeating  them. 


*  Jour.  Am.  Ch.  Soc.,  Vol.  XXV,  p.  896. 


173155 


EXPERIMENTAL  PART. 

COPPER. 
i.  FROM  ALUMINIUM. 

(a)  In  sulphuric  acid  solution. — Dilution  125  cc.,  o.i  cc. 
of   sulphuric  acid    (Sp.  G.  1.83),  N.DIOO  =  4-5    amperes 
and  14 — 8  volts.     Time  10  minutes. 

Copper  present  0.2696  gram,  aluminium  0.2500  gram. 
Copper  found  0.2696  gram-o.2696  gram-o.2695  gram. 

Like  all  deposits  from  this  electrolyte  they  were  some- 
what spongy  but  perfectly  adherent.  On  increasing  the 
amount  of  sulphuric  acid  to  i  cc.  the  deposit  was  much 
smoother  and  more  uniform. 

(b)  In  nitric  acid  solution. — Dilution  125  cc.,  i  cc.  of 
nitric   acid    (Sp.  G.  1.43),  N.  DIOO  =  3  amperes  and  4-5 
volts.     Time  20  minutes. 

Copper  present  0.2874  gram,  aluminium  0.2500  gram. 
Copper  found  0.2873  gram-o.2874  gram-o.2874  gram. 

The  conditions  given  here  were  most  satisfactory  for 
copper  in  this  electrolyte.  A  speed  of  300-400  revolutions 
per  minute  is  best.  Too  high  a  speed  or  less  time  gives  a 
low  result. 

(c)  In  phosphoric  acid  solution. — Dilution  125  cc.,  10  cc. 
of  phosphoric  acid  (Sp.  G.  1.085),  50  cc.  of  a  10%  solution 
of  Na2HPO4,  N.DIOO  =  5  amperes  and  6  volts.     Time  10 
minutes. 

Copper  present  0.2742  gram,  aluminium  0.2500  gram. 
Copper  found  0.2741  gram-o.2742  gram-o.274i  gram. 

The  conditions  recorded  here  gave  the  best  deposits. 
They  were  spongy  in  appearance  but  perfectly  adherent 
and  were  washed  with  ease.  On  dissolving  them  in  nitric 
acid  and  testing  with  an  ammonium  molybdate  solution, 
a  slight  deposit  of  ammonium  phospho-molybdate  was 

(5) 


obtained  in  every  case.  This  amount  of  phosphorus  was 
so  slight,  however,  that  it  would  not  affect  the  weight  of 
the  deposit  materially. 

2.  FROM  ANTIMONY. 

(a)  In  tartrate  solution. — Dilution  125  cc.,  8  grams  of 
tartaric  acid,  25  cc.  of  ammonia,  N.DIOO  =  5  amperes  and 
5  volts.  Time  10  minutes. 

Copper  present  0.2742  gram,  antimony  0.2500  gram. 

This  experiment  resulted  in  the  precipitation  of  nearly 
all  of  the  antimony  with  the  copper. 

3.  FROM  ARSENIC. 

(a)  In  ammoniacal  solution. — Dilution  125  cc.,  25  cc.  of 
ammonia,  2.5    grams  of   ammonium   nitrate,  N.DIOO  =  5 
amperes  and  7  volts.     Time  15  minutes. 

Copper  present  0.2742  gram,  arsenic  o. 2  500  gram.     Cop- 
per found  0.2740  gram-o.274i  gram-o.274i  gram. 
The  deposit  was  dark  in  color,  smooth  and  adherent. 

(b)  In  nitric  acid  solution. — The  conditions  were  the 
same  as  were  used  in  the  separation   of  copper  from 
aluminium. 

Copper  present  0.2742  gram,  arsenic  o. 2 500  gram.  Cop- 
per found  .2741  gram-.2742  gram-.2742  gram. 

4.  FROM  CADMIUM. 

(a)  In  nitric  acid  solution. — The  same  conditions  were 
used  as  in  the  separation  of  copper  from  aluminium. 

Copper  present  0.2742  gram,  cadmium  0.2500  gram. 
Copper  found  0.2742  gram-o.2742  gram-o.2742  gram. 

5.  FROM  CHROMIUM. 

(a)  In  sulphuric  acid  solution. — The  same  conditions 
were  used  as  in  the  separation  of  copper  from  aluminium. 

Copper  present  0.2890  gram,  chromium  0.2500  gram. 
Copper  found  0.2890  gram-o.289i  gram-o.289o  gram. 


Better  deposits  were  obtained  by  starting  the  current 
at  3  amperes  and  raising  gradually  to  5  amperes. 

(6)  In  nitric  acid  solution. — The  same  conditions  were 
used  as  in  the  separation  of  copper  from  aluminium. 

Copper  present  0.2874  gram,  chromium  0.2500  gram. 
Copper  found  0.2874  gram-o.2875  gram-o.2874  gram. 

If  the  current  was  allowed  to  run  above  3  amperes  the 
deposit  weighed  too  high.  A  blank  was  run  with  chro- 
mium alone  under  the  same  conditions,  which  gave  0.0022 
gram  of  a  metal  showing  all  the  tests  for  chromium. 

(c)  In  phosphoric  acid  solution. — The  same  conditions 
were  used  as  in  the  separation  of  copper  from  aluminium. 

Copper  present  0.2742  gram,  chromium  0.2500  gram. 
Copper  found  0.2742  gram-o.274o  gram-o.2742  gram. 

Slight  traces  of  phosphorus  were  found  in  the  deposits. 

6.  FROM  COBALT. 

(a)  In  nitric  acid  solution. — The  same  conditions  w^ere 
observed  as  in  the  separation  of  copper  from  aluminium. 

Copper  present  0.2874  gram,  cobalt  0.2500  gram.  Cop- 
per found  0.2875  gram-o.2874  gram-o.2874  gram. 

Cobalt  was  partially  deposited  in  sulphuric  acid  and 
phosphoric  acid  electrolvte. 

7.  FROM  IRON. 

(a)  In  sulphuric  acid  solution. — The  same  conditions 
were  used  as  in  the  separation  of  copper  from  aluminium. 

Copper  present  0.2696  gram,  iron  0.2500  gram.  Copper 
found  0.2694  gram-o.2695  gram-o.2696  gram-o.2696 
gram-o.2695  gram. 

(6)  In  nitric  acid  solution. — The  same  conditions  were 
observed  as  in  the  separation  of  copper  from  aluminium. 

Copper  present  0.2874  gram,  iron  0.2500  gram.  Copper 
found  0.2873  gram-o.2875  gram-o.2874  gram. 

(c)  In  phosphoric  acid  solution. — The  same  conditions 
were  used  as  in  the  separation  of  copper  from  aluminium. 


8 

Copper  present  0.2742  gram,  iron  o.2Soc  gram.  Copper 
found  0.2743  gram-o.274i  gram-o.2742  gram,  with  8 
amperes  in  5  minutes.  Cu  =  0.2741  gram. 

Slight  traces  of  phosphorus  were  found  in  these  deposits. 

8.  FROM  LEAD. 

(a)  In  nitric  acid  solution. — The  results  were  low.  Lead 
seems  to  hold  back  the  last  traces  of  copper. 

9.  FROM  MAGNESIUM. 

(a)  In  sulphuric  acid  solution. — The  same  conditions 
were  used  as  in  the  separation  of  copper  from  aluminium. 

Copper  present  0.2696  gram,  magnesium  0.2500  gram. 
Copper  found  0.2696  gram-o.2696  gram-o.2695  gram. 

(b)  In  nitric  acid  solution. — The  same  conditions  were 
used  as  in  the  separation  of  copper  and  aluminium. 

Copper  present  0.2874  gram,  magnesium  0.2500  gram. 
Copper  found  0.2874  gram-o.2874  gram-o.2875  gram. 

If  the  current  was  allowed  to  run  too  high  a  white  de- 
posit was  obtained  which  dissolved  in  sulphuric  acid 
without  effervescence.  A  neutral  solution  of  Mg.  (NC>3)2 
acidified  with  one  drop  of  nitric  acid  and  electrolyzed 
with  a  current  2-3  amperes  and  15  volts  for  20  minutes 
gave  a  white  coating  weighing  0.0334  gram. 

(b)  In  phosphoric  acid  solution. — The  same  conditions 
were  used  as  in  the  separation  of  copper  from  aluminium. 

Copper  present  0.2742  gram,  magnesium  0.2500  gram.. 
Copper  found  0.2742  gram-o.274o  gram-o.2742  gram. 

10.  FROM  MANGANESE. 

(a)  In  sulphuric  acid  solution. — The  same  conditions 
were  used  as  in  the  separation  of  copper  from  aluminium. 

Copper  present  0.2890  gram,  manganese  0.2500  gram. 
Copper  found  0.2890  gram-o.289i  gram-o.289o  gram. 

(b)  In  nitric  acid  solution. — The  same  conditions  were 
observed  as  in  the  separation  of  copper  from  aluminium. 


Copper  present  0.2874  gram,  manganese  0.2500  gram. 
Copper  found  0.2872  gram-o.2874  gram-o.2874  gram. 

Only  a  part  of  the  manganese  was  deposited  as  peroxide 
on  the  anode,  but  no  floating  particles  were  observed  in 
the  liquid. 

11.  FROM  NICKEL. 

(a)  In  sulphuric  acid  solution. — No  satisfactory  deposits 
were  obtained.     All  conditions  were  tried.     The  nickel 
seems  to  hold  the  copper  back  when  they  are  present  in 
equal  amounts.     When  the  copper  is  greatly  in  excess  it 
carries  the  nickel  down  with  it. 

(b)  In  nitric  acid  solution. — See  the  thesis  of  Exner.* 

(c)  In   phosphoric   acid   solution. — Nickel   is   partially 
deposited  in  this  electrolyte. 

12.  FROM  URANIUM. 

(a)  In  sulphuric  acid  solution. — The  same  conditions 
were  used  as  in  the  separation  of  copper  from  aluminium. 

Copper  present  0.2890  gram,  uranium  0.2500  gram. 
Copper  found  0.2889  gram-o.289o  gram-o.289o  gram. 

(b)  In  nitric  acid  solution. — The  same  conditions  were 
observed  as  in  the  separation  of  copper  from  aluminium. 

Copper  present  0.2742  gram,  uranium  0.2500  gram. 
Copper  found  0.2742  gram-o.274i  gram-o.2742  gram. 

13.  FROM  ZINC. 

(a)  In  sulphuric  acid  solution. — Dilution  125  cc.,  i  cc. 
of  sulphuric  acid  (Sp.  G.  1.83),  N.DIOO  =  3-5  amperes  and 
5  volts.  Time  10  minutes. 

Copper  present  0.2890  gram,  zinc  0.2500  gram.  Copper 
found  0.2890  gram — 0.2889  gram-o.2889  gram-o.289o 
gram-o.2888  gram. 

The  current  was  raised  gradually.  The  deposits  were 
excellent. 

*  Jour.  Am.  Ch.  Soc.,  Vol.  XXV,  p.  896. 


JO 

(b)  In  nitric  acid  solution. — See  the  thesis  of  Exner.* 

(c)  In  phosphoric  acid  solution  — The  same  conditions 
were  observed  as  in  the  separation  of  copper  from  alumin- 
ium. 

Copper  present  0.2635  gram,  zinc  0.2500  gram.  Copper 
found  0.2635  gram-o.2633  gram-o.2634  gram. 

Slight  traces  of  phosphorus  were  found  in  these  deposits. 

CADMIUM. 

1.  FROM  ALUMINIUM. 

(a)  In  sulphuric  acid  solution. — Dilution  125  cc.,  i  cc. 
of  sulphuric  acid  (Sp.  G.  1.83),  N.DIOO=  5  amperes  and 
5  volts.     Time  10  minutes. 

Cadmium  present  0.2727  gram,  aluminium  0.2500  gram. 
Cadmium  found  0.2728  gram-o.2727  gram-o.2727  gram. 

The  deposits  were  excellent,  although  slightly  spongy, 
but  perfectly  adherent. 

(b)  In  phosphoric  acid  solution. — Dilution  125  cc.,  10  cc. 
of  phosphoric  acid  (Sp.  G.  1.083),  50  cc.  of  a  10%  solution 
of  Na2HPO4,  N.DIOO  =  5  amperes  and  7  volts.     Time  10 
minutes. 

Cadmium  present  0.3032  gram,  aluminium  0.2500  gram. 
Cadmium  found  0.3031  gram-o.3032  gram-o.3032  gram. 
These  deposits  all  showed  slight  traces  of  phosphorus. 

2.  FROM  CHROMIUM. 

(a)  In  sulphuric  acid  solution. — A  beautiful  silver  white 
crystalline    deposit    of    cadmium    was    obtained,    which 
always  weighed  low. 

(b)  In  phosphoric  acid  solution. — The   same  conditions 
were  observed  as  in  the  separation  of  cadmium  from 
aluminium. 

Cadmium  present  0.3600  gram,  chromium  0.2500  gram. 
Cadmium  found  0.3603  gram-o.36oo  gram-o.36oo  gram. 

*  Jotir.  Am.  Ch.  Soc.,  Vol.  XXV,  p.  896. 


II 

3.  FROM  COBALT. 

(a)  In    sulphuric    acid    solution. — Cobalt    is    partially 
precipitated  in  this  electrolyte. 

(b)  In   phosphoric    acid    solution. — Cobalt  is    partially 
precipitated  in  this  electrolyte. 

4.  FROM  IRON. 

(a)  In  sulphuric  acid  solution. — The  same  conditions 
were  used  as  in  the  separation  of  cadmium  from  alumin- 
ium. 

Cadmium  present  0.3032  gram,  iron  0.2500  gram.  Cad- 
mium found  0.3031  gram-o.3032  gram-o.3032  gram. 

(b)  In  phosphoric  acid  solution. — The  same  conditions 
were  used  as  in  the  separation  of  cadmium  from  alumin- 
ium. 

Cadmium  present  0.3032  gram,  iron  0.2500  gram.  Cad- 
mium found  0.3032  gram-o.3O3i  gram-o.3032  gram. 

5.  FROM  MAGNESIUM. 

(a)  In  sulphuric  acid  solution. — The  same  conditions 
were  observed  as  in  the  separation  of  cadmium  from  alu- 
minium. 

Cadmium  present  0.2727  gram,  magnesium  0.2500  gram. 
Cadmium  found  0.2727  gram-o.2728  gram-o.2727  gram. 

(b)  In  phosphoric  acid  solution. — The  same  conditions 
were  used  as  in  the  separation  of  cadmium  from  alumin- 
ium. 

Cadmium  present  0.3600  gram,  magnesium  0.2500  gram. 
Cadmium  found  0.3600  gram-o.3599  gram-o.36oo  gram. 

6.  FROM  MANGANESE. 

(a)  In  sulphuric  acid  solution. — The  same  conditions 
were  used  as  in  the  separation  of  cadmium  from  alumin- 
ium. 

Cadmium  present  0.2727  gram,  manganese  0.2500  gram. 
Cadmium  found  0.2725  gram-o.2727  gram-o.2727  gram. 


12 

(b)  In  phosphoric  acid  solution. — The  same  conditions 
were  used  as  in  the  separation  of  cadmium  from  alumin- 
ium. 

Cadmium  present  0.3600  gram,  manganese  0.2500  gram. 
Cadmium  found  0.3600  gram-o.36oi  gram-o.36oo  gram. 

7.  FROM  NICKEL. 

(a)  In  sulphuric  acid  solution. — The  same  conditions 
were  used  as  in  the  separation  of  cadmium  from  alumin- 
ium. 

Cadmium  present  0.2727  gram,  nickel  0.2500  gram. 
Cadmium  found  0.2727  gram-o.2727  gram-o.2726  gram. 

(b)  In  phosphoric  acid  solution. — The  nickel  was  partially 
precipitated  in  this  electrolyte. 

8.  FROM  ZINC. 

Zinc  always  came  down  with  the  cadmium  in  sulphuric 
acid  solution  and  also  in  phosphoric  acid  solution. 

SILVER. 

1.  FROM  ALUMINIUM. 

In  nitric  acid  solution. — Dilution  125  cc.,  i  cc.  of  nitric 
acid  (Sp.  G.  1.43),  N.DIOO  =  3  amperes  and  3.5  volts. 
Time  15  minutes. 

Silver  present  0.2600  gram,  aluminium  0.2500  gram. 
Silver  found  0.2600  gram-o.2599  gram-o.26oo  gram. 

The  deposits  obtained  in  this  electrolyte  were  very  poor. 
The  addition  of  ammonium  nitrate  helped  matters  but 
little.  Great  care  was  necessary  in  washing  not  to  lose 
some  of  the  deposit. 

2.  FROM  CADMIUM. 

(a)  In  nitric  acid  solution. — Conditions  same  as  No.  i. 
Silver  present   0.2600   gram,    cadmium   0.2500   gram. 
Silver  found  0.2600  gram-o.2598  gram-o.26oi  gram. 


13 

3.  FROM  CHROMIUM. 

(a)  In  nitric  acid  solution. — Conditions  same  as  No.  i. 
Silver  present  0.2600  gram,   chromium  0.2500  gram. 
Silver  found  0.2601  gram-o.2598  gram-o.26oo  gram. 

4.  FROM  COBALT. 

(a)  In  nitric  acid  solution. — Conditions  same  as  No.  i. 
Silver  present  0.2600  gram,  cobalt  0.2500  gram. 
Silver  found  0.2600  gram-o.2598  gram-o.26oo  gram. 

5.  FROM  IRON. 

(a)  In  nitric  acid  solution. — Conditions  same  as  No.  i . 
Silver  present  0.2600  gram,  iron  0.2500  gram.     Silver 
found  0.2599  gram-o.26oo  gram-o.26oo  gram. 

6.  FROM  LEAD. 

(a)  In  nitric  acid  solution. — Conditions  same  as  No.  i. 
Silver  present  0.2600  gram,  lead  0.2500  gram.     Silver 
found  0.2596  gram-o.26oi  gram-o.26oo  gram. 

7.  FROM  MAGNESIUM. 

(a)  In  nitric  acid  solution. — Conditions  same  as  No.  i . 
Silver  present  0.2600  gram,  magnesium  0.2500  gram. 
Silver  found  0.2599  gram-o.26oo  gram-o.26oo  gram. 

8.  FROM  MANGANESE. 

(a)  In  nitric  acid  solution. — Conditions  same  as  No.  i . 
Silver  present  0.2600  gram,  manganese  0.2500  gram. 
Silver  found  0.2600  gram-o.26oo  gram-o.2599  gram. 

9.  FROM  NICKEL. 

(a)  In  nitric  acid  solution. — Conditions  same  as  No.  i. 
Silver  present  0.2600  gram,  nickel  0.2500  gram.     Silver 
found  0.2599  gram-o.2599  gram-o.26oo  gram. 


10.  FROM  ZINC. 

(a)  In  nitric  acid  solution. — Conditions  same  as  No.  i . 

Silver  present  0.2600  gram,  zinc  0.2500  gram.  Silver 
found  0.2601  gram-o.2598  gram-o.26oo  gram. 

Silver  was  also  tried  in  potassium  cyanide  solution— 
but  owing  to  the  great  number  of  metals  deposited  from 
this  electrolyte  and  the  high  current  density  used  with 
the  rotating  anode  no  success  was  attained. 

MERCURY. 

While  mercury  itself  is  easily  determined  by  the  rotating 
anode,  it  is  almost  impossible  to  make  any  separations  of 
it  from  other  metals,  owing  to  the  readiness  with  which 
the  metal  forms  amalgams. 

Aluminium  and  magnesium  were  the  only  successful 
separations.  From  both  of  these  metals  the  mercury  was 
deposited  in  beautiful  mirror-like  form. 

Iron,  chromium,  nickel,  cobalt,  zinc,  manganese  and 
cadmium  were  tried  in  both  sulphuric  and  nitric  acid 
solutions  without  success. 


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